The invention relates to hematologic analyzers which permit samples of blood products to be analyzed automatically.
It relates more particularly to a device for agitating and for taking samples of blood products from tubes which are closed by stoppers and which are grouped together in racks.
Before taking a blood product sample from a tube in order to subject it to analysis, it is essential to agitate the tube so as to mix the constituents of the product and thereby obtain a sample whose composition is homogeneous and representative of the product.
U.S. Pat. No. 3,231,244 discloses an automatic device for mixing blood products, said device comprising a rotary drum which is equipped with receiving seats which are capable of supporting tubes containing such products. The tubes are disposed radially with respect to the axis of rotation of the drum, such that their respective stoppers point outward. This is exclusively an agitating device, and it has the disadvantage that the tubes have to be loaded manually on the drum, and then withdrawn manually from the drum once agitation has been carried out.
Devices for agitating movable tube holders have also been available on the market for many years now. These tube holders have a U configuration in which the tubes are disposed side by side in non-predefined positions and are held by elastic means. This again is exclusively an agitating device, the principal disadvantage of which is that it necessitates manual operations, in particular with respect to loading the tube holders prior to agitation and unloading them after agitation.
Furthermore, EP-A-0,061,317 discloses a device for agitating and for taking samples of blood products, in which device the tubes containing the products are grouped together in racks, and the latter are disposed manually in a rotary drum. This drum has the function of ensuring, by means of rotation, the mixing of the blood products, and of immobilizing a rack in a substantially vertical position so that the tubes which it contains are immobilized with their stoppers facing downward. This device additionally comprises a sampling station which is displaceable in translation underneath the drum and parallel to its axis of rotation, this sampling station being equipped with a sampling needle which is able to take a sample from a tube in a rack after piercing the stopper of the tube, and to perform this sampling operation successively in a series of tubes. After analysis, the racks are withdrawn manually from the drum.
The principal disadvantage of this known device is that it cannot turn the drum, and thus agitate all the tubes, during the actual sampling operation itself. Moreover; the sampling station has to perform a multiplicity of translational displacements, in both directions, which fact leads to mechanical wear and tear. Furthermore, since the sampling is performed directly from a tube in a rack which is immobilized by the drum, it is necessary to provide strong, powerful mechanical members so that the drum remains completely immobile, in particular during the piercing of the stopper of each tube by the sampling needle.
A device for the transfer, agitation and sampling of blood products from tubes which are grouped together in racks is also known from the publication WO 93/25,885 of the Applicant, which device comprises a rotary support capable of holding a plurality of racks and of ensuring their mixing, by rotation, as well as a sampling station which is displaceable in translation and which is able to take a sample from a tube of a rack when the support is immobilized.
This device has basically the same disadvantages as those mentioned above, although, by contrast, it permits complete automation since it comprises transfer means which automatically load the racks on the rotary support with a view to taking samples, and automatically eject the racks from the rotary support after sampling.
Furthermore, U.S. Pat. No. 4,921,676 discloses a device for agitating and for taking samples of blood products from closed tubes which are grouped together in racks. The latter are brought one by one, without being agitated, into line with a mechanism which takes hold of the tubes contained in the rack individually, removes them from the rack, agitates them by partial rotation at a limited angle, and conveys them to a sampling station which is equipped with a needle, before replacing them in the rack.
The principal disadvantage of this device is that it does not agitate the products contained in the tubes for a sufficient length of time. Moreover, the structure and the kinematics of the mechanism for displacing the tubes are particularly complex, and its cost price is therefore high.
It must also be noted that all the devices mentioned above have the disadvantage that the analysis rates which they permit are not sufficiently fast from the point of view of the requirements of present-day laboratories.